<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>experience</title>
</head>
<body>
  <form class="fr" action="">
    <label class="fr__label" for="face-rating">How was your experience?</label>
    <div class="fr__face" role="img" aria-label="Straight face">
      <div class="fr__face-right-eye" data-right></div>
      <div class="fr__face-left-eye" data-left></div>
      <div class="fr__face-mouth-lower" data-mouth-lower></div>
      <div class="fr__face-mouth-upper" data-mouth-upper></div>
    </div>
    <input class="fr__input" id="face-rating" type="range" value="2.5" min="0" max="5" step="0.1">
  </form>
</body>
<style>
  * {
  border: 0;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
:root {
  --hue: 223;
  --white: hsl(var(--hue),10%,100%);
  --lt-gray: hsl(var(--hue),10%,95%);
  --gray1: hsl(var(--hue),10%,90%);
  --gray2: hsl(var(--hue),10%,80%);
  --gray7: hsl(var(--hue),10%,30%);
  --gray9: hsl(var(--hue),10%,10%);
  --primary: hsl(var(--hue),90%,55%);
  --trans-dur: 0.3s;
  font-size: calc(16px + (24 - 16) * (100vw - 320px) / (1280 - 320));
}
body,
input {
  font: 1em/1.5 "DM Sans", sans-serif;
}
body {
  background-color: var(--white);
  color: var(--gray9);
  height: 100vh;
  display: grid;
  place-items: center;
  transition:
    background-color var(--trans-dur),
    color var(--trans-dur);
}

/* Main styles */
.fr {
  animation: fade-slide-in 0.6s ease-out;
  padding: 0 1.5em;
  max-width: 20em;
}
.fr__face {
  --face-hue1: 60;
  --face-hue2: 30;
  background-image:
    linear-gradient(
      135deg,
      hsl(var(--face-hue1),90%,55%),
      hsl(var(--face-hue2),90%,45%)
    );
  border-radius: 50%;
  box-shadow: 0 0.5em 0.75em hsla(var(--face-hue2),90%,55%,0.3);
  margin: 0 auto 2em;
  position: relative;
  width: 3em;
  height: 3em;
}
.fr__face-right-eye,
.fr__face-left-eye,
.fr__face-mouth-lower,
.fr__face-mouth-upper {
  position: absolute;
  transition:
    background-color var(--trans-dur),
    box-shadow var(--trans-dur),
    color var(--trans-dur);
}
.fr__face-right-eye,
.fr__face-left-eye {
  background-color: var(--white);
  border-radius: 50%;
  top: 0.75em;
  width: 0.6em;
  height: 0.6em;
}
.fr__face-right-eye {
  --delay-right: 0s;
  animation: right-eye 1s var(--delay-right) linear paused;
  clip-path: polygon(0 75%,100% 0,100% 100%,0 100%);
  left: 0.6em;
}
.fr__face-left-eye {
  --delay-left: 0s;
  animation: left-eye 1s var(--delay-left) linear paused;
  clip-path: polygon(0 0,100% 75%,100% 100%,0 100%);
  right: 0.6em;
}
.fr__face-mouth-lower,
.fr__face-mouth-upper {
  color: var(--white);
  top: 1.75em;
  left: 0.75em;
  width: 1.5em;
  height: 0.75em;
}
.fr__face-mouth-lower {
  --delay-mouth-lower: 0s;
  animation: mouth-lower 1s var(--delay-mouth-lower) linear paused;
  border-radius: 50% 50% 0 0 / 100% 100% 0 0;
  box-shadow: 0 0.125em 0 inset;
}
.fr__face-mouth-upper {
  --delay-mouth-upper: 0s;
  animation: mouth-upper 1s var(--delay-mouth-upper) linear paused;
  border-radius: 0 0 50% 50% / 0 0 100% 100%;
  box-shadow: 0 -0.125em 0 inset;
}
.fr__label {
  display: block;
  margin-bottom: 1.5em;
  text-align: center;
}
.fr__input {
  --input-hue: 60;
  --percent: 50%;
  background-color: var(--gray1);
  background-image: linear-gradient(hsl(var(--input-hue),90%,45%),hsl(var(--input-hue),90%,45%));
  background-size: var(--percent) 100%;
  background-repeat: no-repeat;
  border-radius: 0.25em;
  display: block;
  margin: 0.5em auto;
  width: 100%;
  max-width: 10em;
  height: 0.5em;
  transition: background-color var(--trans-dur);
  -webkit-appearance: none;
  appearance: none;
  -webkit-tap-highlight-color: transparent;
}
.fr__input:focus {
  outline: transparent;
}

/* WebKit */
.fr__input::-webkit-slider-thumb {
  background-color: var(--white);
  border: 0;
  border-radius: 50%;
  box-shadow: 0 0.125em 0.5em hsl(0,0%,0%,0.3);
  width: 1.5em;
  height: 1.5em;
  transition: background-color 0.15s linear;
  -webkit-appearance: none;
  appearance: none;
}
.fr__input:focus::-webkit-slider-thumb,
.fr__input::-webkit-slider-thumb:hover {
  background-color: var(--lt-gray);
}

/* Firefox */
.fr__input::-moz-range-thumb {
  background-color: var(--white);
  border: 0;
  border-radius: 50%;
  box-shadow: 0 0.125em 0.5em hsl(0,0%,0%,0.3);
  width: 1.5em;
  height: 1.5em;
  transition: background-color 0.15s linear;
}
.fr__input:focus::-moz-range-thumb,
.fr__input::-moz-range-thumb:hover {
  background-color: var(--lt-gray);
}

/* `:focus-visible` support */
@supports selector(:focus-visible) {
  .fr__input:focus::-webkit-slider-thumb {
    background-color: var(--white);
  }
  .fr__input:focus-visible::-webkit-slider-thumb,
  .fr__input::-webkit-slider-thumb:hover {
    background-color: var(--lt-gray);
  }
  .fr__input:focus::-moz-range-thumb {
    background-color: var(--white);
  }
  .fr__input:focus-visible::-moz-range-thumb,
  .fr__input::-moz-range-thumb:hover {
    background-color: var(--lt-gray);
  }
}

/* Dark theme */
@media (prefers-color-scheme: dark) {
  body {
    background-color: var(--gray9);
    color: var(--gray1);
  }
  .fr__face-right-eye,
  .fr__face-left-eye {
    background-color: var(--gray9);
  }
  .fr__face-mouth-lower,
  .fr__face-mouth-upper {
    color: var(--gray9);
  }
  .fr__input {
    background-color: var(--gray7);
  }
}

/* Animations */
@keyframes fade-slide-in {
  from,
  16.67% {
    opacity: 0;
    transform: translateY(25%);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}
@keyframes right-eye {
  from { clip-path: polygon(0 75%,100% 0,100% 100%,0 100%); }
  50%, to { clip-path: polygon(0 0,100% 0,100% 100%,0 100%); }
}
@keyframes left-eye {
  from { clip-path: polygon(0 0,100% 75%,100% 100%,0 100%); }
  50%, to { clip-path: polygon(0 0,100% 0,100% 100%,0 100%); }
}
@keyframes mouth-lower {
  from {
    border-radius: 50% 50% 0 0 / 100% 100% 0 0;
    top: 1.75em;
    height: 0.75em;
    visibility: visible;
  }
  40% {
    border-radius: 50% 50% 0 0 / 100% 100% 0 0;
    top: 1.95em;
    height: 0.25em;
    visibility: visible;
  }
  50%,
  to {
    border-radius: 0;
    top: 2em;
    height: 0.125em;
    visibility: hidden;
  }
}
@keyframes mouth-upper {
  from,
  50% {
    border-radius: 0;
    box-shadow: 0 -0.125em 0 inset;
    top: 2em;
    height: 0.125em;
    visibility: hidden;
  }
  62.5% {
    border-radius: 0 0 50% 50% / 0 0 100% 100%;
    box-shadow: 0 -0.125em 0 inset;
    top: 1.95em;
    height: 0.25em;
    visibility: visible;
  }
  75% {
    border-radius: 0 0 50% 50% / 0 0 100% 100%;
    box-shadow: 0 -0.125em 0 inset;
    top: 1.825em;
    height: 0.5em;
    visibility: visible;
  }
  to {
    border-radius: 0 0 50% 50% / 0 0 100% 100%;
    box-shadow: 0 -0.8em 0 inset;
    top: 1.75em;
    height: 0.75em;
    visibility: visible;
  }
}
</style>
<script>
  window.addEventListener("DOMContentLoaded",() => {
  const fr = new FaceRating("#face-rating");
});

class FaceRating {
  constructor(qs) {
    this.input = document.querySelector(qs);
    this.input?.addEventListener("input",this.update.bind(this));
    this.face = this.input?.previousElementSibling;
    this.update();
  }
  update(e) {
    let value = this.input.defaultValue;

    // when manually set
    if (e) value = e.target?.value;
    // when initiated
    else this.input.value = value;

    const min = this.input.min || 0;
    const max = this.input.max || 100;
    const percentRaw = (value - min) / (max - min) * 100;
    const percent = +percentRaw.toFixed(2);

    this.input?.style.setProperty("--percent",`${percent}%`);

    // face and range fill colors
    const maxHue = 120;
    const hueExtend = 30;
    const hue = Math.round(maxHue * percent / 100);

    let hue2 = hue - hueExtend;
    if (hue2 < 0) hue2 += 360;

    const hues = [hue,hue2];
    hues.forEach((h,i) => {
      this.face?.style.setProperty(`--face-hue${i + 1}`,h);
    });

    this.input?.style.setProperty("--input-hue",hue);

    // emotions
    const duration = 1;
    const delay = -(duration * 0.99) * percent / 100;
    const parts = ["right","left","mouth-lower","mouth-upper"];

    parts.forEach(p => {
      const el = this.face?.querySelector(`[data-${p}]`);
      el?.style.setProperty(`--delay-${p}`,`${delay}s`);
    });

    // aria label
    const faces = [
      "Sad face",
      "Slightly sad face",
      "Straight face",
      "Slightly happy face",
      "Happy face"
    ];
    let faceIndex = Math.floor(faces.length * percent / 100);
    if (faceIndex === faces.length) --faceIndex;

    this.face?.setAttribute("aria-label",faces[faceIndex]);
  }
}
</script>
</html>